I suspect there's some sort of effort underway, but I suspect there's a lot of work to be done in rebalancing and partially redesigning the old plans. As you point out, SS1 plans aren't compatible with SS2. That likely means that it's necessary to load up the plan with SS1, scrap all the plots, then export the structures that remain, so that that template can be loaded with SS2. Then it's a matter of replicating the plot placement and building plan selections, and if the original plans haven't been ported to SS2, selecting replacements that fit the theme and fill the same role. Finally, there's the need for rebalancing food, water, and jobs, since plot yields are different and recreational plots counted as jobs in SS1 but don't in SS2.
So yeah. Might happen eventually, but it's going to be a pretty big undertaking, and would probably get put on the back burner as long as new chapter content is being focused on.
